A temporal, time, or time-travel paradox is a logical contradiction or paradox that appears to be inherent in at least one of the theoretical scenarios suggested by the supposition that "time travel" into the past is possible. These include at least three hypothetical or fictional forms of backward causation mediated by "time travel" from one time to a time in its past:

the bootstrap and predestination paradoxes, where, respectively, the existence of an object, or the occurrence of an event, would be construed as existing or occurring only because of the (backward) influence on it of what might be called "its later self"

the grandfather paradox, where an event, that presupposes a specific earlier event, prevents it, by its (backward) influence on the earlier event